Inorganic Approach to Stabilizing Nanoscale Toroidicity in a Tetraicosanuclear Fe${}_{18}$Dy${}_6$ Single Molecule Magnet

Cyclic coordination clusters (CCCs) are proving to provide an extra dimension in terms of exotic magnetic behavior as a result of their finite but cyclized chain structures. The Fe${}_{18}$Dy${}_6$ CCC is a Single Molecule Magnet with the highest nuclearity among Ln containing clusters. The three isostructural compounds [Fe${}_{18}$Ln${}_6$(μ-OH)${}_6$(ampd)${}_{12}$(Hampd)${}_{12}$(PhCO${}_2$)${}_{24}$](NO${}_3$)${}_6$·38MeCN for Ln = Dy${}^{III}$ (1), Lu${}^{III}$ (2), or Y${}^{III}$ (3), where H${}_2^{-}$ampd = 2-amino-2-methyl-1,3-propanediol, are reported. These can be described in terms of the cyclization of six {Fe${}_3$Ln(μOH)(ampd)${}_2$(Hampd)${}_2$(PhCO${}_2$)${}_4$}${}^{+}$ units with six nitrate counterions to give the neutral cluster. The overall structure consists of two giant Dy${}_3$ triangles sandwiching a strongly antiferromagnetically coupled Fe${}_{18}$ ring, leading to a toroidal arrangement of the anisotropy axis of the Dy ions, making this the biggest toroidal arrangement on a molecular level known so far.